Chang Rongguang, an 82-year-old stamp collector, shows the first day cover with stamps released to mark the 40th anniversary of China's reform and opening up at a post office in Xicheng District of Beijing, capital of China, Dec. 18, 2018. China Post released a set of commemorative stamps and one souvenir sheet marking the 40th anniversary of China's reform and opening up on Tuesday. (Xinhua/Li He)